Decomposition of cumene hydroperoxide and recovery of boron trifluoride catalyst

ABSTRACT

Cumene hydroperoxide is decomposed to phenol and acetone using boron trifluoride or a boron trifluoride complex as the decomposition catalyst. The boron trifluoride in the reaction product is reacted with a phosphorus-containing salt of an alkali metal such as sodium phosphate for recovery and reuse in the process.

FIELD OF THE INVENTION

This invention relates to the catalytic cleavage of cumene hydroperoxideto equal molar portions of phenol and acetone using boron trifluoride asthe catalyst, and more particularly it relates to a process for thecatalytic cleavage of cumene hydroperoxide in the presence of borontrifluoride or a complex of boron trifluoride with an oxygen-containingpolar compound in which the boron trifluoride in the product isdeactivated by reaction with a phosphorus-containing salt of an alkalimetal. The boron trifluoride is subsequently recovered from the complexformed with this phosphorus-containing salt such as sodium phosphate andis recycled to the process.

DESCRIPTION OF THE PRIOR ART

Cumene can be readily oxidized with air to form cumene hydroperoxide andthe hydroperoxide can then be decomposed to form equal molar amounts ofphenol and acetone. In the commercial process for producing phenol bythis general method, a small amount of a mineral acid, generallysulfuric acid, is used as the decomposition or cleavage catalyst. Sincephenol and acetone are the products of the cleavage reaction, thereaction solvent can conveniently be a phenol-acetone solution. In thisprocess the cumene hydroperoxide instantaneously decomposes to phenoland acetone as it is slowly added in solution with cumene to the mineralacid solution. The highly exothermic reaction is controlled by the rateof cumene hydroperoxide addition and by acetone reflux. Water issubstantially excluded from the reaction medium during the decompositionreaction to insure homogeneity. Since the mineral acid is neutralized inthe product stream with an alkali solution to reduce tar formationduring subsequent distillative separation of the phenol and acetone fromthe tars, the resulting alkali sulfate sludge by-product must bedisposed of and new acid must be continuously supplied to the process.

DESCRIPTION OF THE INVENTION

The desired decomposition of cumene hydroperoxide is a cleavage to equalmols of phenol and acetone, that is, about 62 weight percent phenol and38 weight percent acetone. In using sulfuric acid as the decompositioncatalyst, a selectivity to phenol of about 85 to 95 percent is generallyobtained. The non-selective decomposition product particularly ascatalyzed by a strong mineral acid includes cumyl alcohol, acetophenone,methylbenzofuran, several organic acids, mono- and dicumylphenol,diacetone alcohol, acetol, mesityl oxide, phorone, alpha-methylstyreneand various oligomers of alpha-methylstyrene which are tar-likesubstances. When the reaction product is distilled, these by-productsremain in the residue which is collectively called "tar" or "tars". Ithas been reported that the main products in this "tar" are cumylphenoland dicumylphenol, the polymers of alpha-methylstyrene, acetophenone anddiacetone alcohol. Since few of these by-products of the non-selectivereaction can be economically recovered, this non-selective reactionrepresents a significant economic loss.

A particular advantage in the use of the boron trifluoride and complexedboron trifluoride decomposition catalysts is that a selectivity greaterthan 95 percent, approaching 100 percent under optimum conditions, canbe obtained. Another advantage of these catalysts in contrast with thestrong mineral acid catalyst is that the boron trifluoride catalysts donot promote the alkylation of phenol product to cumylphenol nor theoligomerization of aromatic olefin to form tars. Furthermore, in thepresent process the major by-product, if any, alpha-methylstyrene, canbe recovered and hydrogenated to cumene for recycle in the process. Afurther advantage in the use of the boron trifluoride catalysts insteadof the mineral acid catalysts is that the corrosion problems of thelatter are substantially avoided.

The mineral acid in the crude decomposition product resulting from themineral acid catalyzed cleavage reaction is deactivated byneutralization with a suitable basic substance prior to distillation ofthe crude mixture for the separation of the phenol and acetone productfrom the tar, otherwise the mineral acid will catalyze substantialadditional tar formation during distillation. Thus, we have determinedthat distillation of a portion of a sulfuric acid catalyzeddecomposition product resulted in 12 percent tar while only 4.4 percenttar resulted overall in another portion of the same decompositionproduct which was distilled after neutralization with sodiumbicarbonate. But this neutralization procedure, which includesdownstream caustic and acid washes, introduces water into the reactionproduct. This requires additional distillation equipment for waterremoval and requires additional treatment of the separated water forphenol removal prior to its disposal. A separator is also required forthe removal of precipitated sodium sulfate. A substantial economicburden is superimposed onto the mineral acid-catalyzed decompositionprocess including capital, labor and energy costs as a result of thecatalyst neutralization and associated procedures.

In contrast, in the present procedure, the catalyst is deactivated forproduct distillation in a non-aqueous procedure by reacting the borontrifluoride catalyst with a phosphorus-containing salt to form a stablecoordination compound. This coordination compound will not decompose atthe temperatures required to distill off the products and by-productsfrom the product solution but it can be decomposed at highertemperatures. As a result, neutralization and water removal problems areeliminated from the system and product separation is greatly simplified.And most advantageously the complex of the boron trifluoride and thephosphorus-containing salt can be decomposed after product separation,to release both the phosphorus-containing salt and the boron trifluoridefor separate recovery and recycle in the process. This recovery of borontrifluoride not only provides an economic saving, but it alsosubstantially reduces environmental problems which would result fromdischarging it as a waste.

The phosphorus-containing salts which we find to be suitable forcomplexing with the boron trifluoride are the alkali metal phosphatesand alkali metal pyrophosphates. Of particular suitability are sodiumphosphate, Na₃ PO₄ ; sodium pyrophosphate, Na₄ P₂ O₇ ; potassiumphosphate, K₃ PO₄ and potassium pyrophosphate, K₄ P₂ O₇. The primaryfunction of this phosphorus-containing salt is to produce a sufficientlystrong complex with the boron trifluoride to retain the borontrifluoride in the residue resulting from the product distillationnotwithstanding rigorous distillation conditions.

When boron trifluoride gas is used as the catalyst, it can be bubbledinto the reaction liquid or the desired quantity can be added to thefree space in the reactor from which it will readily dissolve in thereaction liquid. We have found that catalyst concentration is animportant reaction variable. That is, the higher the catalystconcentration, the more rapid the reaction until too much catalystrenders the exothermic reaction uncontrollable. On the other hand, thereaction is too slow with too little catalyst. Within these constraintsthe concentration of non-complexed boron trifluoride catalyst willgenerally be between about 20 parts of boron trifluoride per millionparts of total reaction liquid (ppm.), and about one percent, or evenhigher with appropriate control of reaction temperature and preferablyits concentration will be between about 500 ppm. and about 0.5 percent.

The complexed boron trifluoride catalyst is a liquid or solid which isreadily dissolved in the reaction liquid. Suitable complexes can beformed with boron trifluoride and water or an appropriateoxygen-containing organic polar compound in which oxygen acts as theelectron donor. These organic polar compounds include aliphatic alcoholshaving one to about four carbon atoms; aromatic alcohols such as benzylalcohol; aliphatic ethers having from two to about eight carbon atoms;or mixed alkyl-aromatic ethers such as methylphenyl ether; aliphaticacids having from one to about four carbon atoms or aromatic acids suchas phenol and benzoic acid; acid anhydrides such as acetic acidanhydride; esters formed from aliphatic acids having from one to aboutfour carbon atoms esterified with an alkyl group containing one to aboutfour carbon atoms or with an aromatic group such as phenyl and benzyl;an aliphatic ketone having from two to about eight carbon atoms, anaromatic ketone such as dibenzyl ketone or a mixed alkyl-aromaticketone; aliphatic aldehydes having from two to about four carbon atomsor an aromatic aldehyde such as benzyl aldehyde; and the like. Alsouseful as a complexing agent for the boron trifluoride are suitablechlorine derivatives of the above such as chloroethyl alcohol,dichloroethyl alcohol, trichloroacetaldehyde, and the like. Free borontrifluoride, which is dissolved in the reaction liquid, readilycomplexes with phenol which is produced as the reaction proceeds.Nevertheless, we have found that the reaction proceeds more rapidly whenfree boron trifluoride is used as the catalyst than when this borontrifluoride complex with phenol is initially used as the catalyst sincethe free boron trifluoride is a much more active catalyst.

The boron trifluoride complex can be either a 1:1 or a 2:1 molar complexof the complexing agent with the boron trifluoride provided that thecomplex can be produced and is stable at the conditions of thedecomposition reaction. The concentration of the boron trifluoride inthe reaction liquid depends, in part, on the properties of the complex.For example, some complexes are active at very low concentrations, whileother complexes require substantially higher amounts for a suitable rateof reaction. The more active complexes of boron trifluoride, such as the1:1 complex with diethyl ether, are similar in activity to free borontrifluoride. The concentration range for free boron trifluoride in thereaction liquid, as specified above, also applies to the complexes ofboron trifluoride.

Since the cleavage reaction is highly exothermic, temperature control ofthe reaction liquid is generally provided. This temperature control canbe accomplished by controlling the amount of catalyst used or bycontrolling the rate at which the catalyst is mixed with the cumenehydroperoxide. But with the highly active catalysts one or both of thefollowing techniques for temperature control is desirably utilized.Temperature control can be effected, in part, by maintaining appropriatemeans for the positive cooling of the reaction liquid during thereaction such as by solvent reflux or by submerged cooling coils.Another effective and useful method of temperature control is theemployment of sufficient inert solvent to serve as a heat sink. Thereaction can be carried out within the range of between about 25° toabout 110° C. and preferably a range of between about 60° to about 80°C. At the lower temperatures the reaction becomes quite slow althoughhighly selective, while undesirable tar formation can result at highertemperatures due to the effects of thermal decomposition of the cumenehydroperoxide.

The pressure within the reactor is not a critical factor during thedecomposition reaction. Generally, the pressure will range from apressure moderately below to moderately above atmospheric pressure.Since boron trifluoride gas is highly soluble in the reaction liquid,the boron trifluoride gas pressure need only be moderately elevatedabove atmospheric pressure to obtain its solution in the liquid reactionmedium.

The cumene hydroperoxide can desirably be prepared by oxidation ofcumene with air in the conventional manner. In this process a solutionof at least about 10 weight percent cumene hydroperoxide in cumene isdesirably produced, although a product containing less than 10 weightpercent cumene hydroperoxide can be utilized. Since it is notparticularly desirable to use an excessive amount of cumene in acontinuous process as a reaction solvent due to subsequent handling andseparation problems, it is preferred that a more concentrated solutionof cumene hydroperoxide be prepared. In this oxidation reaction themaximum concentration of cumene hydroperoxide that can conveniently beproduced is about 30 percent.

The cumene hydroperoxide to be used in the decomposition reaction can befurther concentrated by flashing off sufficient cumene to form a feedsolution of between about 60 to about 90 percent, preferably about 65 toabout 80 percent, cumene hydroperoxide. Although pure cumenehydroperoxide can be used, it is not desirable to obtain it in thisfinal stage of purity for economic reasons and also for safety reasonssince the presence of some cumene tends to stabilize the cumenehydroperoxide. The decomposition reaction can suitably be carried outwith as little as about 0.1 weight percent cumene hydroperoxide in thereaction liquid, with at least about 0.5 percent being preferred and atleast about 1.0 percent being most preferred. The maximum amount ofcumene hydroperoxide in the cleavage reaction liquid will suitably beabout 20 weight percent, preferably about 10 percent and most preferablyabout 5 percent. Since explosions have in the past resulted from cumenehydroperoxide reactions which have run away, it is generally desired tocarry out the reaction with substantial diluent as a safety measure,resulting in a concentration of cumene hydroperoxide in the reactionliquid much below the upper limit.

The solvent used in this process can be the cumene associated with thecumene hydroperoxide as described above. However, since phenol andacetone are the desired reaction product, a phenol-acetone solvent isgenerally desirable in order to simplify product separation. Since asolution of cumene hydroperoxide and cumene is usually added to thereactor, the solvent system will therefore include cumene as acomponent, generally a minor component. The solvent can conveniently bethe 1:1 molar phenol to acetone product of the cumene hydroperoxidecleavage reaction, however, variations in the relative proportions canbe used. Thus, although there is no particular advantage to using anexcess of phenol, an excess of acetone may be desirable, particularly ifthe acetone is to be utilized for temperature maintenance duringreaction by means of acetone reflux or boil-off. Therefore, the molratio of acetone to phenol as the solvent in the reaction mixture can beas high as about 10:1 and preferably no higher than about 3:1. Otherusable solvents include aromatic solvents such as benzene, toluene, andthe like; ethers such as diethyl ether and tetrahydrofuran, or any othersolvent which is compatible with the reactant and catalyst and can beconveniently separated.

Phenol is not inert when used as a solvent for cumene hydroperoxide inits decomposition. Rather phenol, by virtue of its acid nature, has beenfound to be a catalyst for the decomposition of cumene hydroperoxide ina reaction which is significantly slower than the above-describedmineral acid catalyzed reaction. Moreover, the selectivity of thisphenol catalyzed decomposition of cumene hydroperoxide is very poor,being less than 80 percent selectivity to phenol as determined by astudy of the reaction. It is readily apparent that the presence ofsolvent phenol in the mineral acid catalyzed reaction of the commercialprocesses is not noticeably detrimental because the great speed of themineral acid catalyzed decomposition effectively eliminates thedetrimental effect on selectivity of the relatively slow phenolcatalyzed reaction. In our reaction we can avoid a significant adverseeffect on product selectivity from the phenol catalyzed reaction,particularly when phenol is present as an added solvent, by appropriatecatalyst selection and/or concentration to obtain a suitably rapidreaction.

When operating under the general conditions described herein,particularly within a temperature range between about 60° and 80° C.,the decomposition reaction to substantial completion, as a batch or as acontinuous process, will take place in about two minutes to about twohours, and preferably will take place in about five to about 45 minutes.The process can also be carried out in a semi-continuous manner in whichthe reactant, solvent and catalyst are continuously added to a stirredtank reactor at a rate coinciding with the withdrawal rate, sufficientto provide a suitable average reaction rate within the above time rangesfor substantially complete reaction. Since a significant quantity ofunreacted cumene hydroperoxide in the final reaction product canundesirably interfere with the distillative separation procedure, it ispreferred that there be a substantially complete decomposition of thecumene hydroperoxide in the reaction stage.

After the cumene hydroperoxide decomposition reaction is completed, theproduct solution is treated with the alkali metal phosphate orpyrophosphate in order to bind the boron trifluoride with this salt in astable coordination compound. If the catalyst is boron trifluorideitself, the phosphorus-containing salt directly reacts with the borontrifluoride to form the complex. If the catalyst is a coordinationcompound of boron trifluoride and the oxygen-containing polar compound,the phosphorus-containing salt will react with this catalyst complexdisplacing and freeing the oxygen-containing polar compound. Thephosphate or pyrophosphate salt is able to displace theoxygen-containing polar compound from its complex with the borontrifluoride because the complex of this salt with boron trifluoride isthe stronger and more stable complex.

The phosphate salt can complex with from one to three mols of borontrifluoride while the pyrophosphate salt can complex with from one tofour mols of the same. At least about a stoichiometric amount of thesalt should be added to tie up the boron trifluoride, that is, at leastabout 0.25 mol of the phosphate salt and at least about 0.33 mol of thepyrophosphate salt per mol of boron trifluoride in the product solution.To insure that all of the boron trifluoride is complexed so that thereis no carry-over of it into the distillate it is preferred that anexcess of either salt be used, that is, at least about 0.4 mol of thephosphate or pyrophosphate salt be used per mol of boron trifluoride upto a molar ratio of 1:1 or higher, such as 5:1, but such excess amountsmay be of no particular advantage.

The product solution is then distilled under appropriate conditions oftemperature and pressure to drive off the volatile components in thesolution including acetophenone without dissociating the complex ofboron trifluoride with the phosphorus-containing salt. Under theseconditions of operation the only materials remaining in the still arethe complex and the polymeric tar solids. The temperature in the stillis then elevated to the decomposition temperature of the complex, orhigher, to dissociate the complex and volatilize the boron trifluoridefor separate recovery. The phosphate or pyrophosphate salt is recoveredfrom the residue by dissolving the salt in water.

It may be desirable in certain instances to distill off the volatilecompounds in the reaction product, including acetophenone, at a reducedpressure and temperature to improve the separation of the acetophenoneand minimize formation of tars during distillation. For these reasonsthis distillation can be carried out at a temperature as low as about150° C. and a pressure of about one millimeter of mercury, but it ispreferred to use distillation conditions of at least about 160° C. and apressure of at least about 30 mm Hg. and most preferably a distillationtemperature of at least about 200° C. is used. If distillation iscarried out at about atmospheric pressure (760 mm. Hg.), the temperaturemust be at least as high as the boiling point of acetophenone (201.7°C.). A pressure higher than atmospheric pressure can be used in thedistillation but there is no advantage to using such elevated pressures.The distillation can be effected at a temperature up to about thedecomposition temperature of the coordination compound, but preferablydistillation conditions should be maintained substantially below thistemperature to avoid any dissociation of this complex and carry-over ofboron trifluoride into the distillate.

After this distillation is completed, the residue containing thecoordination compound and the polymeric tar solids is further heated todissociate the boron trifluoride from the phosphate or pyrophosphatesalt for separate recovery of these two components. This decompositioncan be accomplished by heating the residue to the decompositiontemperature of the particular complex, but preferably higher andcondensing out the volatilized boron trifluoride in a cold trap. If thisdecomposition temperature is sufficiently high as to cause a partialdecomposition and distillation of the polymeric tar solids, then it isnecessary to separate out and recover the boron trifluoride from thedistillation vapors.

DESCRIPTION OF PREFERRED EMBODIMENTS

In the following examples, the hydroperoxide was analyzed by iodometrictitration with sodium thiosulfate. The boron analysis was carried out byconverting the boron to a water soluble acid or salt and thenquantitatively measuring it by atomic absorption. The decompositionproduct resulting from the boron trifluoride, both free and complexed,catalyzed reactions was light yellow in color and transparent,indicating very slight tar, while the sulfuric acid catalyzed productliquid was black and opaque. Both the residue and the product distillatewere analyzed. Many of the analyses in the following examples add up to100 percent due to product averaging becuse the actual "tar" value wasless than one percent as indicated where specific tar analyses weremade. The analyses for compounds other than hydroperoxide and boron wereaccomplished by gas chromatography or by high performance liquidchromatography.

EXAMPLE 1

The catalytic activity of sulfuric acid for the decomposition of cumenehydroperoxide was observed. A 57.3 percent solution of cumenehydroperoxide in cumene was added dropwise into 100 ml. of a two percentsolution of sulfuric acid in acetone in a 300 ml. round bottom flaskopen to the atmosphere. Each drop instantly decomposed as it contactedthe solution. Since no positive cooling of the reaction liquid wasprovided, the temperature of the solution rose from room temperature(about 25° C.) at the beginning of the addition to 44° C. upon thecompletion of the addition. A total of 35.2 g. of the cumenehydroperoxide was added over 60 minutes. Analysis of the product showedthat 99.9 percent of the cumene hydroperoxide had reacted at aselectivity of 93 percent to phenol.

EXAMPLE 2

The following reactions were carried out in a glass reactor equippedwith a magnetic stirrer and operated at a pressure within the reactorslightly above atmospheric pressure. The reactor was cooled by a coldfinger in the liquid. Small samples of the reaction liquid (about 1 ml.)were periodically withdrawn to monitor the reaction.

Phenol was tested as a decomposition catalyst for cumene hydroperoxideat several temperatures. About 20 g. of a solution consisting of 5 partsphenol, 3 parts acetone and 1 part cumene were placed in the reactor.About 2 ml. of a solution consisting of 55 percent cumene hydroperoxidein cumene were injected into the reactor in each experiment. Table Isummarizes the results of these experiments.

                  TABLE I                                                         ______________________________________                                                 Cumene Hydroperoxide Decomposed, %                                            Minutes                                                              Temp.      10        20        50      100                                    ______________________________________                                        40° C.                                                                            trace     trace     trace   trace                                  60° C.                                                                            --         8        19      39                                     80° C.                                                                            18        34        60      85                                     ______________________________________                                    

The experiment at 80° C. was allowed to run for four and one-half hoursat which time the cumene hydroperoxide was completely decomposed.Analysis of this product mixture disclosed that it contained 77 percentphenol, 8 percent alpha-methylstyrene, 4 percent acetophenone, 4 percentdimethylbenzyl alcohol, and 7 percent of a residuum consisting ofaromatic carbonyls, aromatic alcohols, substituted phenols, substitutedbenzofurans and methylstyrene oligomers.

EXAMPLES 3-5

A 200 ml. glass reactor partially immersed in a heated oil bath at 60°C. and equipped with a magnetic stirrer and a cold finger was used inthese experiments. The cold finger was cooled with tap water and wasonly used when necessary to prevent excessive temperatures. A series ofthree experiments was carried out using different amounts of borontrifluoride gas as the catalyst. The reactor was charged with 22 g. of a20 percent solution of cumene hydroperoxide (CHP) which heated to 60° C.Boron trifluoride gas in a predetermined amount was bubbled into theliquid to initiate the decomposition reaction. One ml. samples weretaken at intervals to monitor completion of the reaction. The results ofthese experiments, after greater than 99 percent decomposition of thecumene hydroperoxide, are set out in Table II.

                  TABLE II                                                        ______________________________________                                        Example          3        4         5                                         ______________________________________                                        CHP solution, g. 22       22        22                                        BF.sub.3 conc., ppm.                                                                           340      136       27                                        Time, min.       <5       30        60                                        Final Temp, ° C.                                                                        100      72        64                                        Selectivity                                                                    phenol          92       90        98                                         alpha-methylstyrene                                                                           3        4         1                                          acetophenone    3        4         1                                          dimethylbenzyl alcohol                                                                        2        2         --                                        ______________________________________                                    

EXAMPLES 6-8

A second series of three experiments was conducted using the samereactor and 22 g. of a 20 percent solution of cumene hydroperoxide. Inthese experiments different amounts of a solution of the 1:1 complex ofboron trifluoride with diethyl ether in acetone, at a concentration ofone ml. per liter of acetone, were added, after the cumene hydroperoxidesolution had reached 60° C., to initiate the decomposition reaction. Oneml. samples were taken at intervals to monitor the reaction. The resultsof these experiments are set out in Table III.

                  TABLE III                                                       ______________________________________                                        Example           6        7        8                                         ______________________________________                                        CHP solution, g.  22       22       22                                        BF.sub.3 . O(Et).sub.2, conc., ppm.                                                             200      100      50                                        Time, min.        <3       5        8                                         Final temp., ° C.                                                                        85       82       80                                        CHP decomp., %    99       99       99                                        Selectivity                                                                    phenol           97       98       98                                         alpha-methylstyrene                                                                            2        1        1                                          acetophenone     1        1        1                                         ______________________________________                                    

EXAMPLE 9

A charge of 22 g. of the 20 percent solution of cumene hydroperoxide wasplaced in the reactor. After the solution had reached 60° C., one ml. ofa solution of the 1:1 complex of boron trifluoride with isopropanol inacetone, at a concentration of 14 ml. per liter of acetone, was added toprovide a concentration of 400 ppm. of the catalyst in the reactor.Complete decomposition of the cumene hydroperoxide occurred in aboutthirty minutes at a final temperature of 69° C. Analysis of the productdisclosed a selectivity to phenol of 97 percent, to alpha-methylstyreneof 1.8 percent, to acetophenone of 0.7 percent and to dimethylbenzylalcohol of 0.5 percent.

EXAMPLE 10

Another 22 g. charge of the 20 percent cumene hydroperoxide solution wasplaced in the reactor. After the solution had been warmed to 60° C., asufficient quantity of a solution of the 1:2 complex of borontrifluoride with methanol in acetone, at a concentration of two ml. perliter of acetone, was added to provide a concentration of 104 ppm. ofthe boron trifluoride dimethanol complex in the reactor. Completedecomposition of the hydroperoxide was obtained in 45 minutes at a finaltemperature of 74° C. The selectivity to phenol was 97.5 percent, toalpha-methylstyrene two percent and to acetophenone 0.5 percent.

EXAMPLE 11

After a 22 g. charge of 20 percent cumene hydroperoxide had heated to60° C., a 1:1 complex of boron trifluoride and phenol was introduced insufficient amount to provide 435 ppm. of the catalyst complex. A maximumtemperature of 67° C. was reached and complete decomposition occurred in60 minutes at a selectivity of 97 percent to phenol, two percent toalpha-methylstyrene and one percent to acetophenone.

EXAMPLE 12

A 20 g. charge of a solution consisting of phenol, acetone and cumene inthe weight ratio of 5:3:1, respectively, was placed in the reactor.After adding 1.83 g. of concentrated (80-82 percent) cumenehydroperoxide to the solution, it warmed to 60° C. One ml. of a solutionof the 1:1 complex of boron trifluoride with diethyl ether in acetone,at a concentration of two ml. of the complex per liter of acetone wasadded to provide a concentration of the complex of 90 ppm. based on thetotal solution. Complete decomposition of the cumene hydroperoxideoccurred in ten minutes.

EXAMPLE 13

A continuous flow reaction was carried out in a one liter flask equippedwith a reflux column and a magnetic stirrer. About 300 ml. of acetonewere added to the flask and warmed to 60° C. The catalyst, a solution ofboron trifluoride monodiethyletherate complex in acetone, was pumpedinto the flask at a rate of about 350 ml. per hour, which provided a 0.3percent concentration of the complex in the reaction liquid.Concentrated (80-82 percent cumene hydroperoxide in cumene was added ata rate of 750 ml. per hour. Product was continuously removed at a rateto maintain the liquid volume constant. Acetone was continuouslydistilled off and returned to the flask by reflux to maintain a flasktemperature between 60° and 70° C. By analysis of the product stream,there was found to have been better than 99 percent conversion at aselectivity of about 98 percent to phenol, about two percent toalpha-methylstyrene and about one percent to acetophenone.

EXAMPLE 14

A solution containing 0.16 g. of the 1:1 complex of boron trifluorideand diethylether was heated to 60° C. and 20.46 g. of 80 percent cumenehydroperoxide was added slowly to control the temperature. Aftercompletion of the reaction, the solution was distilled at about 100 mm.Hg. pressure at a temperature ranging from 45° to 160° C. The distillateand tar were analyzed for boron. The analysis showed that there was 18.1mg. of tar in the crude solution prior to the distillation and 14.3 mg.in the distillate and 4.3 mg., i.e. 23.8 percent, in the tar afterdistillation.

EXAMPLE 15

A 20 percent solution of cumene hydroperoxide in cumene was slowly addedto 19.46 grams of an acetone solution of the 1:1 complex of borontrifluoride with diethylether containing 11.87 mg. of boron, maintainedat about 60° C. with constant reflux, until 26.0 grams of thehydroperoxide solution was added. After the cumene hydroperoxide wascompletely decomposed, it was analyzed for boron and was found tocontain 11.63 mg. of boron. A 2.0 gram quantity of sodium pyrophosphatewas added to this product solution. The volatiles were distilled off ata maximum temperature of 160° C. and 100 mm. Hg. An analysis of the tarresidue in the still found 11.37 mg. of boron in this residue, which was95.3 percent of the boron introduced into the reactor. Upon raising thestill pot temperature to about 400° C., the resulting boron trifluoridevapors condense out in a -196° C. trap.

EXAMPLE 16

An 80 percent solution of cumene hydroperoxide in cumene is slowly addedto 0.16 gram of the 1:1 complex of boron trifluoride with diethyletherin 14.0 grams of acetone at about 60° C. until 20.0 grams of theconcentrated hydroperoxide solution have been added. After completedecomposition, the product solution is treated with 4.5 grams of sodiumphosphate and heated for about 30 minutes at 50° C. to insure that theboron trifluoride complexes with the phosphate salt. The mixture isdistilled at a temperature of about 160° C. and a pressure of about 100mm. Hg. After the acetone, the phenol and the distillable by-productsincluding acetophenone have been taken overhead, the residue containingthe polymeric tars and the boron trifluoride complex is heated to about400° C. The volatilized boron trifluoride is condensed in a trap cooledto -196° C. The tar is washed with water and the sodium phosphate isrecovered from the water for reuse.

It is possible by appropriate correlation and control of the variousvariables involved in this process to minimize tar formation andoptimize boron trifluoride recovery during the cumene hydroperoxidedecomposition and the product separation stages.

It is to be understood that the above disclosure is by way of exampleand that numerous modifications and variations are available to those ofordinary skill in the art without departing from the true spirit andscope of the invention.

We claim:
 1. The method for cleaving cumene hydroperoxide at highselectivity to phenol and acetone which comprises the steps(a)contacting a solution comprising about 0.1 to about 20 weight percentcumene hydroperoxide with a catalytic amount of boron trifluoride, aboron trifluoride complex with water or a boron trifluoride complex withan oxygen-containing polar organic compound at a temperature betweenabout 25° and about 110° C. until the cleavage of said cumenehydroperoxide is substantially completed, (b) deactivating said catalystby adding at least a stoichiometric amount of an alkali metal phosphateor alkali metal pyrophosphate whereby a coordination compound of saidboron trifluoride and said alkali metal phosphate or alkali metalpyrophosphate is formed, (c) distilling the product solution at atemperature and a pressure whereby all components of the productsolution are substantially distilled over except the said coordinationcompound of boron trifluoride with the said alkali metal phosphate orpyrophosphate and the polymeric tar solids formed during the cleavagereaction or during said distillation, (d) heating the residue to atleast the decomposition temperature of the said coordination compound ofboron trifluoride with the said alkali metal phosphate or pyrophosphateto dissociate said coordination compound and volatilize the borontrifluoride and (e) recovering said dissociated boron trifluoride. 2.The method for cleaving cumene hydroperoxide at high selectivity tophenol and acetone in accordance with claim 1 in which the catalyst is acomplex of boron trifluoride with water, a dialkyl ether having betweentwo and about eight carbon atoms or an alkyl alcohol having between oneand about four carbon atoms and the catalyst is present in an amountbetween about 20 ppm. and about one weight percent.
 3. The method forcleaving cumene hydroperoxide at high selectivity to phenol and acetonein accordance with claim 1 in which the solution comprises phenol andacetone in a mol ratio between about 1:1 and about 1.10 and betweenabout one and about five weight percent cumene hydroperoxide.
 4. Themethod for cleaving cumene hydroperoxide at high selectivity to phenoland acetone in accordance with claim 1 in which there is between about500 ppm. and about 0.5 weight percent of the catalyst.
 5. The method forcleaving cumene hydroperoxide at high selectivity to phenol and acetonein accordance with claim 1 in which the alkali metal is sodium orpotassium and the dissociated alkali metal phosphate or pyrophosphate isremoved from the said polymeric tar solids by dissolving the said saltin water.
 6. The method for cleaving cumene hydroperoxide at highselectivity to phenol and acetone in accordance with claim 5 in whichsaid distillation is carried out at a temperature of at least about 150°C. up to about the decomposition temperature of said coordinationcompound of boron trifluoride with said sodium or potassium salt.
 7. Themethod for cleaving cumene hydroperoxide at high selectivity to phenoland acetone in accordance with claim 6 in which the distillation iscarried out at a pressure between about 1.0 mm. Hg. and aboutatmospheric pressure.
 8. The method for cleaving cumene hydroperoxide athigh selectivity to phenol and acetone in accordance with claim 7 inwhich the distillation is carried out at a temperature of at least about160° C. and a pressure of at least about 30 mm. Hg.
 9. The method forcleaving cumene hydroperoxide at high selectivity to phenol and acetonein accordance with claim 6 in which the distillation is carried out at atemperature substantially below the said decomposition temperature. 10.The method for cleaving cumene hydroperoxide at high selectivity tophenol and acetone in accordance with claim 5 in which at least about astoichiometric amount of said phosphate salt is added to form a 1:3molar coordination compound with the boron trifluoride or at least abouta stoichiometric amount of said pyrophosphate salt is added to form a1:4 molar coordination compound with the boron trifluoride.
 11. Themethod for cleaving cumene hydroperoxide at high selectivity to phenoland acetone in accordance with claim 10 in which a substantial molarexcess of the said phosphate or pyrophosphate salt is added over theminimum amount required to complex with all of the boron trifluoride.12. The method for cleaving cumene hydroperoxide at high selectivity tophenol and acetone in accordance with claim 5 in which the molar ratioof the phosphate or pyrophosphate salt and the boron trifluoride is atleast about 1:1.
 13. The method for cleaving cumene hydroperoxide athigh selectivity to phenol and acetone in accordance with claim 5 inwhich the molar ratio of the phosphate or pyrophosphate salt and theboron trifluoride is between about 0.4:1 and about 5:1.